I actually just watched the Little Mermaid yesterday (I love Disney movies and Ariel was one of my favorites when I was little). So I would say that Ursula is unusable, too much association. But besides that, I just don't like the sound of it anyway.

I see both the good and bad of Ursula. Who knows how much the Little Mermaid will mean to the generation that your little one will grow up with? The association could be faded a bit by then. You might want to consider Ursuline or Ursulina as alternatives if you are bothered by it.

"Don't try to be modern, it's the most old-fashioned thing there is," - Attilio, The Tiger and the Snow

Well, 'The Little Mermaid' is one of those Disney classics, so I doubt there will be that many children in the newer gens that don't know of or haven't seen 'The Little Mermaid'. That being said, I still think it's pretty usable. And I think it sounds pretty cool.